The contamination of consumable food products, both for humans and animals including pet food, animal feed, packaged food meals, raw produce, meat and poultry etc. is a major source of economic and commercial damage, emotional and physical distress and is of concern to public health and wellbeing. One common cause of such contamination is from microbial organisms, namely bacteria and fungi, that can cause spoilage, poisoning, and other adverse health effects resulting in serious health conditions and even death for both humans and animals. This, and other cases of microbial infection outbreaks, has created a significant demand for developing technologies to allow a rapid and cost effective technique of detecting the presence of such microbial organisms, without the need of specialized training, throughout the production supply chain, to the consumer.1,2 
Current microbial detection techniques rely mostly on isolation and culturing of the various microbial samples or the use of immunoassays (fluorescent and radioactive) to detect macromolecules associated with various bacterial species. Enzyme-linked immunosorbent assay (ELISA) is another derivative technique where enzymes are attached to the antibody to produce more detectable products. Other detection techniques utilize mass spectroscopy techniques in combination with gas chromatography, and pyrolysis methods to detect bacterial byproducts. Flow cytometry can also be used for rapid detection, identification and separation of cells. Total luminescence spectroscopy can also detect cells quite rapidly. A number of these techniques, for example, are mentioned by U.S. Pat. No. 7,889,334 B2, U.S. Pat. No. 8,501,414 B2, US Pat. Pub. No. 20130084586, and European Pat. Pub. No. 1712614 A1.
However, these techniques are often costly, labor intensive, require significant training and skills by the operator and can require the use of a laboratory (culturing of bacteria), expensive equipment (mass spectrometers, fluorescence microscopes) and chemicals (fluorescent and or radioactive chemical labels, antibodies etc.) that make their routine implementation for unskilled persons, consumers, and other areas of the supply chain impractical. The techniques also result in the destruction or contamination of the food sample rendering it unfit for further consumption.
Other approaches to detecting bacteria involve the use of nanostructures.3 More commonly nanoparticles have been used for signal enhancements, as well as bio-sensing and detection systems to identify microorganism specific molecules by the detection of biological binding events of specific ligands, anti-bodies, chemical labels or analytes4. This nanostructure approach to bio-sensing is based on attaching a ligand, or a chemical or biological label, to the nanostructures, which upon interacting either chemically or physically with the target molecule(s) will result in changing the electrical or optical properties of the sensor substrate. This can potentially offer several advantages including limited hands-on time, real-time analysis as well as label-free detection methods and devices4. Known examples of this approach (which differ significantly when compared to the biological sensing of the present disclosure) include nanostructures of gold, silver4 and zinc oxide.5 
Zinc oxide is a popular choice from a materials perspective for the fabrication of nanostructures due to its catalytic, electrical, optoelectronic, and piezoelectric properties.6-11 
This detection methodology using nanostructures for biological sensing while advantageous, also suffers from limitations. These include the assumption that the presence of certain molecules indicates active microbial presence, specificity to particular species of microbes or molecules, requiring multiple tests to detect more than one microbial species or molecules. The isolation and coating of the ligands onto the nanostructures can be very costly depending on the type of ligand used.
This approach to bio sensing is the current paradigm in the scientific and patent literature, with the assumption that these nanostructures are inadequate for biological sensing without the coating of ligands onto the nanostructure to discern the binding of specific analytes and thus the biological organism.